JPH10330673A - Erasing ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an erasing ink composition capable of producing handwriting easily erasable by rubbing with an eraser and having improved usability and applicability to all kinds of paper by compounding a specific coloring agent, a rubber latex and water as essential components. SOLUTION: This composition contains a coloring agent, a rubber latex and water as essential components. The coloring agent is obtained by dispersing colored fine particles, which consist of microcapsules enclosing a coloring matter selected from an oil-soluble dye, a dispersing dye and a pigment or microcapsules enclosing an oily medium supporting the coloring matter in a homogeneous state, in an aqueous medium containing rubber latex. Preferably, the colored fine particles are microcapsules having an average particle diameter of 0.1-10 μm, and they are used in the range of 1-30 wt.% of the ink composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an erasable ink composition for writing which provides a handwriting which is easily erased by rubbing with an eraser on a sheet of paper.

[0002]

2. Description of the Related Art There have been many proposals for this kind of erasable ink for writing. For example, Japanese Patent Application Laid-Open No. 5-214285 proposes an erasable ink composition containing a resin having a film-forming temperature or a glass transition temperature of 0 ° C. or lower and a pigment. However, since the ink of the present invention uses a pigment as a colorant, the pigment particles in the ink easily penetrate between paper fibers when written on the paper surface. Therefore, although a large amount of filler is used or the surface of special processed paper coated on the surface, for example, art paper, copy paper, etc., gives an eraser-erasable handwriting, it is used for high-quality paper and Handwriting tends to be difficult to erase on paper such as newsprint, and is not applicable to all papers.

[0003]

SUMMARY OF THE INVENTION The present invention is intended to easily apply not only to a specially processed paper surface coated as described above, but also to general paper surfaces including very commonly used papers by rubbing with an eraser. It is an object of the present invention to provide an erasable ink for writing that provides erasable handwriting.

[0004]

The erasable ink composition of the present invention comprises a colorant, a rubber latex and water as essential components, and the colorant is selected from oil-soluble dyes, disperse dyes and pigments. Colored fine particles comprising microcapsules enclosing a dye or microcapsules enclosing an oil-based medium in which the dye is carried in a homogeneous state, wherein the colored fine particles are an aqueous ink dispersed in an aqueous medium containing the rubber latex.

The oil-soluble dye and the disperse dye are selected from dyes classified into a solvent dye and a disperse dye having a color index, respectively, and have chemical structures of azo, metal complex salt azo, anthraquinone and metal phthalocyanine. It is a dye having. The pigment is an inorganic pigment such as an azo-based, anthraquinone-based, condensed polyazo-based, thioindigo-based, metal complex salt-based, phthalocyanine-based, perinone-based, perylene-based, dioxazine-based and quinacridone-based organic pigment, carbon black, or iron oxide. . The oily medium is soluble in some volatile organic solvent, and is water-insoluble;
It is a non-volatile or non-volatile liquid or solid substance at room temperature, and is used as a carrier for maintaining the dye in a homogeneous state. Substances used as the oily medium include monobasic acid esters, dibasic acid mono- or diesters, esters such as partial or complete esters of polyhydric alcohols, aromatic hydrocarbons such as alkylbenzene and alkylnaphthalene, higher alcohols, It is a single or a mixture of two or more selected from aliphatic hydrocarbons such as paraffin, higher fatty acids, mono or diesters of polyalkylene oxides, ketones and ethers.

The microcapsules are colored fine particles in which the pigment or a colored body obtained by dissolving or dispersing the pigment in an oil medium is encapsulated in a shell composed of a substance forming a wall film by a known microencapsulation method. . Examples of the wall film forming substance forming the shell include gelatin, shellac, gum arabic, rosin, rosin ester, ethyl cellulose, carboxymethyl cellulose, paraffin, tristearin, polyvinyl alcohol, polyethylene, polypropylene, acrylic resin, vinyl resin, Polyisobutene, polyurethane, polybutadiene, polyester, polyamide, epoxy resin, phenol resin, silicone resin, polystyrene, melamine resin and the like can be used alone or in combination. Applicable microencapsulation methods include coacervation method, in-situ polymerization method, interfacial polymerization method, submerged hard coating method, phase separation method from aqueous solution, phase separation method from organic solvent, melt dispersion cooling method, Known methods such as a medium suspension coating method and a spray drying method can be used. The microcapsules applied to the ink of the present invention are colored fine particles having an average particle size in the range of 0.1 μm to 10 μm, and are used in the range of 1 to 30% by weight in the ink composition.

As rubber latex, acrylonitrile / butadiene rubber, carboxylated acrylonitrile /
Acrylonitrile / butadiene rubber latex such as butadiene rubber, methyl methacrylate / butadiene,
Methyl methacrylate / butadiene rubber latex such as carboxylated methyl methacrylate, styrene / butadiene rubber latex such as styrene / butadiene, carboxylated styrene butadiene, acrylate rubber latex, vinyl chloride rubber latex, vinylpyridine / styrene / butadiene rubber Latex, chloroprene rubber latex and the like can be mentioned, and those sold as an aqueous dispersion as a latex emulsion are preferably used. These rubber latexes are contained in the ink composition in an amount of 5 to 60% by weight, preferably 20 to 60% by weight in terms of solid content.
To 50% by weight. If the amount is less than 5% by weight, good handwriting erasability cannot be obtained, and if the amount exceeds 60% by weight, the viscosity of the ink becomes high, making it difficult to use it in a marking pen or ballpoint pen.

[0008] Further, ethylene glycol, propylene glycol, glycerin, hexylene glycol, 1,3-butanediol, and the like as water retention agents for suppressing the evaporation of ink moisture at a pen tip such as a marking pen or a ballpoint pen,
Polyhydric alcohols such as neoprene glycol, lubricants, preservatives, and surfactants for improving the ink fluidity, dispersing, and stabilizing the emulsion are also added as necessary. Further, when the ink of the present invention is applied to an aqueous ballpoint pen having a simple structure without an ink flow control member in the pen, a viscous ink imparted with thixotropic properties with a polysaccharide such as xanthan gum, welan gum, succinoglycan, etc. Used as When these polysaccharides are added, they are added in the range of 0.1 to 0.8% by weight in the ink composition.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The erasable ink composition of the present invention comprises:
A mixture of a dispersion of colored fine particles (microcapsules containing pigment), a rubber latex and a predetermined amount of water prepared by the known microencapsulation method is dispersed, stirred for about 1 hour, and further added with additives. Obtained by stirring for about 2 hours.

[0010]

【Example】

1. Preparation of Dispersion of Colored Fine Particles (Dye-Encapsulated Microcapsules) Black Fine Particle Dispersion A 10 g of carbon black processed pigment (Microlith Black CK manufactured by Ciba Geigy) surface-treated with vinyl chloride / vinyl acetate copolymer resin and 2- 10 g of cetyl ethylhexanoate is dispersed and dissolved in 50 g of methyl ethyl ketone, and the carbon black dispersion is treated with Coronate L (polyvalent isocyanate, manufactured by Nippon Polyurethane Industry Co., Ltd.).
g of the mixture and homogenously mixed under heating is emulsified in 60 g of a 5% aqueous solution of polyvinyl alcohol heated to about 70 ° C. using a homomixer so as to form microdroplets of 0.5 to 1.0 μm. While stirring the obtained emulsion, a solution in which 1 g of diethylenetriamine is dissolved in 24 g of water is dripped little by little over about 30 minutes. Subsequently, the liquid temperature was raised to 80 ° C., and stirring was continued for about 3 hours, so that methyl ethyl ketone was volatilized to obtain the black fine particle dispersion liquid A containing the carbon black / 2-ethylhexanoate dispersion. The black fine particles in this dispersion had an average particle size of 3.0 μm.
m.

Black Fine Particle Dispersion B Black Solvent Dye (CI Solvent Black 2)
7) Dissolve 20 g in 60 g of methyl ethyl ketone, add 10 g of an epoxy resin (bisphenol A / diglycidyl ether type, epoxy equivalent: 184 to 194) to the solution, and heat and uniformly mix the mixture at about 70 ° C. 0.1% in 50 g of warm 5% aqueous polyvinyl alcohol solution.
The mixture is emulsified with a homomixer so as to form fine droplets of 5 to 1.5 μm. While stirring the obtained emulsion, 2.5 g of an epoxy resin curing agent (aliphatic polyamine) was added thereto with 22.5 of water.
The solution dissolved in g is dripped little by little over about 1 hour. Subsequently, the liquid temperature was raised to 80 ° C. and stirring was continued for about 5 hours, whereby methyl ethyl ketone was volatilized to obtain the black fine particle dispersion liquid B containing the black solvent dye. The black fine particles in this dispersion had an average particle size of 1.0 μm.

Red Fine Particle Dispersion 10 g of an azo red pigment surface-treated with a vinyl chloride / vinyl acetate copolymer resin and 10 g of stearyl myristate
Was dispersed and dissolved in 50 g of methyl ethyl ketone, 10 g of Coronate L (polyvalent isocyanate, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to the azo red pigment dispersion, and the mixture was homogeneously mixed under heating at about 70 ° C. 5% warmed to
0.5 to 1.0 in 60 g of polyvinyl alcohol aqueous solution
The mixture is emulsified with a homomixer so as to form micro-droplets. While stirring the obtained emulsion, a solution in which 1 g of diethylenetriamine is dissolved in 24 g of water is dripped little by little over about 30 minutes. Subsequently, the liquid temperature was raised to 80 ° C., and stirring was continued for about 3 hours, whereby methyl ethyl ketone was volatilized to obtain a red fine particle dispersion liquid containing the azo red pigment / stearyl myristate dispersion. The red fine particles in this dispersion had an average particle size of 2.0 μm.

2. Example ink and comparative example ink Table 1 shows the compositions of the example inks and the comparative example inks prepared using the respective colored fine particle dispersions. Here, the inks of Examples 1 to 3 and Comparative Example 1 are examples of inks applied to the marking pen, and the inks of Example 4 and Comparative Example 2 are inks of the ink applied to the water-based ballpoint pen having the simple structure. It is an example. Incidentally, the composition of the comparative example ink is described in
The composition is based on the description in JP-A-214285.

[Table 1]

The details of the contents of the raw materials in the table are described below according to the note numbers. (1) Carbon black MA-100 (Mitsubishi Chemical Corporation)
(2) Styrene-butadiene rubber latex (solid content 7)
0%) (Nipol 4850A, Nippon Zeon Co., Ltd.)
(3) Carboxylated acrylonitrile-butadiene rubber latex (solid content 45%, Nipol LX55
0, manufactured by Zeon Corporation) (4) Acrylate rubber latex (solid content 45%)
(Nipol LX874, manufactured by Nippon Zeon Co., Ltd.) (5) Carboxylated styrene / butadiene rubber latex (solid content: 41%) (Nipol LX432A, manufactured by Nippon Zeon Co., Ltd.) (6) Polyoxyethylene (6 mol) sorbit tetra Oleate (7) Polyoxyethylene alkyl ether phosphate ester / monoethanolamine salt (8) Polyoxyethylene (10 mol) nonyl phenyl ether (9) 3% leozan (product name of Sanshin Co., Ltd.) aqueous dispersion Leozan: Semi-synthetic polysaccharide (succinoglycan)

3. Erasability test of handwriting with sample ink (1) Sample marking pen Marking consists of an aluminum cylinder with a pen holder fixed to a pen body made by binding fiber bundles with resin via a valve mechanism. At times, a marking pen was used in which the pen tip was pressed against the paper to open the valve and the ink in the cylinder was led out to the pen tip. Fill the marking pen with a predetermined amount of the inks of Examples 1 to 3 and Comparative Example 1,
A sample pen was used. (2) Ballpoint pen for sample A cartridge having a ballpoint pen at one end of a polypropylene pipe is filled with a predetermined amount of each of the sample inks of Example 4 and Comparative Example 2, and a ballpoint pen having a simple structure is obtained by inserting the cartridge into a writing shaft. A sample pen was used. (3) Test method Each of the sample pens was used for coating paper, woodfree paper and newsprint.
A predetermined line was drawn on the seed paper, and the obtained handwriting was rubbed with an eraser to determine the degree of difficulty of erasability.

Table 2 shows the test results.

[Table 2] The contents of the handwriting erasability determination symbols in Table 2 are as follows. ：: Easily erased Δ: Slight handwriting remains after 5 to 6 rubs ×: Cannot be erased by 10 rubs

[0017]

The erasable ink composition of the present invention can be used not only on the surface of a coated paper coated with a surface coating but also on the surface of a paper generally used such as high quality paper or newsprint. Scrubbing with an eraser also results in handwriting that is easily erased.

Claims (3)

[Claims] 1. A composition containing a colorant, a rubber latex and water as essential components, wherein the colorant is a microcapsule containing a pigment selected from an oil-soluble dye, a disperse dye and a pigment or a homogeneous state of the pigment. An erasable ink composition comprising colored microparticles formed of microcapsules enclosing an oily medium carried on a substrate, wherein the colored microparticles are dispersed in an aqueous medium containing the rubber latex. 2. The method according to claim 1, wherein the colored fine particles are 0.1 μm to 10 μm.
Microcapsules having an average particle size in the range of
The erasable ink composition according to claim 1, which is used in an amount of 1 to 30% by weight in the ink composition. 3. The colored fine particles are microcapsules enclosing an oily medium carrying the dye in a homogeneous state,
The erasable ink composition according to claim 1, wherein the oil medium is a liquid or solid substance that is soluble in some volatile organic solvent and insoluble in water, and is hardly volatile or nonvolatile at room temperature.